Cutting inserts are well known and a large percentage of them are of the throw away design. Such inserts are detachably clamped on a holder and then are discarded when they become dull or chipped.
The inserts must be securely and accurately held in place within an insert holder during the cutting operation. This is especially true when the inserts are employed with numerically controlled machines which depend for accuracy upon an accurately located and firmly supported insert. When the inserts are of a substantial area, it is possible to fix the insert both accurately and firmly within the pocket of a toolholder by providing the insert with a central hole and the toolholder with a pin-type clamping device. In other cases, such inserts may be held in place by a top clamp. Examples of such holders are found in U.S. Pat. Nos. 3,754,309; 3,399,442 and 3,762,005 and British Patent Specification 1,363,542.
Several toolholding systems designed to work in cooperation with specific insert configurations are available in the metal cutting industry. One example of such a system is the TOP NOTCH brand toolholder and insert combination which is taught in U.S. Pat. No. 3,754,309 and which is manufactured and sold by Kennametal Inc., the assignee of the subject invention. This style of insert which is characterized by a diagonal notch is retained in a three-sided toolholder pocket by means of a clamp arrangement which engages both the notch in the insert and a diagonal recess in the toolholder body.
Another example of a dedicated toolholder-insert system is marketed by the Greenleaf Corporation of Saegertown, Pa. This system employs a toolholder with a female "V" shaped seat in which an insert with a corresponding male "V" bottom is retained by a clamp adjustably held in the toolholder. Iscar Tools LTD., markets a similar toolholder with a female "V" shaped seat in which an insert with a corresponding male "V" bottom is retained. Iscar also a markets a toolholder with an insert-pocket wedge geometry having a female "V" shaped seat on the bottom and a male "V" shaped seat on the top. An insert with corresponding male and female "V" shaped bottom and top portions is passively retained in the pocket. No adjustable clamping arrangement is provided in the Iscar toolholder.
Such a basic toolholder and insert configuration in which a female "V" shaped seat supports a corresponding male "V" bottom shaped insert as described in the aforesaid several examples has achieved a demonstrated level of acceptance and popularity within the metalworking industry. However, it has been discovered that this configuration results in the generation of significant tensive stresses on the toolholder female "V" shaped seat. The stress in made manifest in the spreading which can occur in the female "V" shaped seat over the life of the toolholder. As the seat spreads, the cooperative seating arrangement of the insert in the toolholder diminishes in quality, resulting in a rocking motion of the insert within the female "V" shaped seat of the toolholder. Because of the high degree of accuracy required in metalworking operations, any discrepancy in the actual position of the insert during metalworking operations from its planned and anticipated position can result in irreparable damage to the workpiece. More particularly, the tensive stresses typically exerted upon the prior art toolholders' insert seats by their inserts are significant and these forces ultimately resulted in a reduced accuracy in insert location and positioning during metalworking operations.
The main object of metal machining is the shaping of the new work surface. Much attention is paid to the formation of the chip during the machining process, even through the chip is a waste product. This is because the consumption of energy occurs mainly in the formation and movement of the chip. Also, a chip can turn back into the workpiece and damage the machined finish thereof. This represents significant problem, for example, in machining aluminum wheels in the automotive industry or when deep grooving, profiling or cutting off any material, including synthetics, that produce a continuous chip. Moreover, in certain metal cutting operations it has been found that the chips can cause excessive wear and/or damage to the clamping arrangement and/or toolholder. Thus an essential feature of any metalcutting operation is effective chip control. A principal class of chips is the discontinuous chip which has the practical advantage of being easily cleared from the cutting area. While some metals and alloys generate discontinuous chips during cutting operations, many do not. It is therefore very desirable to produce discontinuous chips during a cutting operation, regardless of the metal or alloy of the workpiece.
It has been a common practice to place a mechanical chip breaking member between the insert and the clamp securing the insert to the tool in order to provide at least a degree of chip control during the cutting operation. This arrangement presents the obvious drawback of increasing the effective area necessary for metal cutting operations with a given tool.
Because chip control is an important consideration in metal cutting operations, it has been a long standing objective in the art of metal cutting to develop improved chip control techniques for use with tools as well as improved designs for the cutting inserts. Among the improvements to the cutting insert are various chip control geometries which can be molded into the insert during manufacture. These geometries include various depressions and elevations on the surface of the insert.
It is an object of the invention to provide an insert with improved chip control characteristics.
It is another object of this invention to provide a method of manufacturing an insert incorporating advanced cutting tool materials and having improved chip control.
It is an object of this invention to provide an improved seating arrangement for an insert and toolholder which results in the controllable and consistent placement of the insert with respect to the toolholder and extends the useful life of the toolholder.
It is still another object of this invention to provide an insert with improved metal cutting capabilities when machining, for example, nonferrous and abrasive materials or other materials, including synthetics that produce a continuous chip.
It is yet another object of this invention to provide an improved chip control insert configured to cooperate with a clamping element of an insert toolholder.
It is still another object of this invention to provide a toolholder with an improved clamping arrangement for use in combination with cutting inserts, chip control features and advanced cutting tool materials.